1. Field of the Invention
The present invention relates to a closure for the filler neck of a container normally filled with fluid, where the fluid is subject to varying pressures and temperatures, e.g., a cooling or hydraulic system.
2. Description of the Related Art
In one known closure, DE-AS No. 1 254 908, the lower portion of a U-shaped tube is provided with a throttling restriction. This lower portion is immersed in fluid in the container to determine the fluid level. Any pressure that may have build up in the space above the fluid, either as a gaseous mixture or as air, can be released through the tube when the closure cap is removed, thereby avoiding ejection of hot fluid directly from the container. A bleed line is provided, but the tube is separated therefrom by two seals when the closure cap is installed. A pressure relief valve also is provided, at the top of the container, but does not have any connection with the bleed line.
This closure has the disadvantage that the throttling restriction permits fluid to enter the tube at all times, and to the height of the fluid in the container. This fluid then is ejected when the closure cap is removed and may injure the operator. In addition, opening of the pressure relief valve may eject fluid, which will cause fluid loss and possibly damage. These disadvantages give rise to the further disadvantage that the fluid level constantly is changing, which may be detrimental to the operation of the fluid system connected to the container.
In another known closure, DE-PS No. 3 007 272, a filler neck is arranged at an angle in the side wall of a coolant radiator to control the fill level of the coolant in the radiator. The space above the collant is filled with air and is connected by a tube to a sealing surface on the filler neck which is sealed by the closure cap. The tube is opened upon removal of the closure cap, establishing a connection between the air space and atmosphere. A pressure relief valve is provided in the closure cap, where it constantly is exposed to the coolant. When the pressure relief valve is opened, it provides a connection by way of a bleed line between the atmosphere and the interior of the radiator.
With this closure, it may be possible to avoid expulsion of hot coolant upon opening of the cap, since the pressure of the coolant is reduced by an initial, partial opening of the closure cap. However, increased coolant level due to heat expansion leads to a flow of the additional volume of coolant through the bleed line. In addition, it is possible to overfill the container with coolant. The coolant then is unable to flow off through the bleed line with the closure cap is installed, as generally occurs immediately after filling.
Although this closure cap represents an improvement over the first case cited above, it does not provide a satisfactory solution as the described disadvantages show.